What is otoscopy?

Otoscopy is an examination that involves looking into the ear with an instrument called an otoscope (or auriscope).

This is performed in order to examine the 'external auditory canal' – the tunnel that leads from the outer ear (pinna) to the eardrum.

Inspection of the eardrum can also provide a lot of information about what's happening within the middle ear – the space within the skull where the hearing and balance mechanisms are situated.

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An otoscope consists of three parts:

the handle, which contains the power for the light source

the head, which contains the light bulb and magnifying lens

the cone, which is inserted into the ear canal.

Inspection of the outer ear

Before inserting the otoscope cone into the ear canal, the outer ear is inspected for any signs of disease that may relate to the patient's symptoms. For example, if the complaint is of ear pain, there may be evidence of an infection of the outer ear in the form of redness or slight swelling.

Examination of the external auditory canal

The examination is performed by gently pulling the outer part of the ear upwards and backwards. This action straightens the external auditory canal, which has a natural curve, and makes it easier to see the eardrum.

The normal external auditory canal has some hair, often lined with yellow to brown wax. The total length of the ear canal in adults is approximately 2cm, which gives it a resonance frequency of approximately 3400 Hz, which is an important frequency region for understanding speech.

Abnormal findings may include:

a dry, flaky lining suggestive of eczema. The usual symptom is of itch.

an inflamed and swollen, narrowed canal, possibly with a discharge indicating infection (otitis externa). The usual symptoms include itch, local discomfort, a discharge and often an unpleasant smell from the ear.

wax obscuring the eardrum.

a foreign body in the ear, such as the rubber from the end of a pencil.

Examination of the eardrum

The normal eardrum appears pinkish-grey in colour and is approximately circular in shape.

The first of the three small bones that transmit sound vibrations to the hearing mechanism (the cochlea) lies against the far side of the drum and can be seen through it in the upper part, like the clock hands in approximately the 12 o'clock position.

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Most otoscopes have a small air vent connection that allows the doctor to puff air in to the canal. Observing how much the eardrum moves with air pressure assesses its mobility, which varies depending on the pressure within the middle ear. This technique is called insufflation.

Normally the air pressure within the middle ear is the same as that in the outer ear. This allows the eardrum to lie in its middle position and respond to sound vibration most efficiently.

Air gets to the middle ear through a short tube, called the Eustachian tube, that leads from the middle ear to a region high on the side wall of the back of the throat. This opening cannot be seen by ordinary inspection because it's behind the roof of the mouth.

Blockage of the Eustachian tube is a common finding in conditions – such as hay fever, a cold or, in children, 'glue ear'.

If blocked, air cannot get to the middle ear to equalise the pressure on the eardrum. This can impair hearing or, if the pressure difference is enough to stretch the eardrum, cause pain. This is the basis of the discomfort you might get when flying with a cold.

A doctor can get some idea of whether the Eustachian tube is blocked by asking you to gently blow out while pinching your nose and closing your lips. This is called Valsalva's manoeuvre, and the normal finding is that the eardrum moves slightly during it. When the Eustachian tube is blocked, the eardrum remains still.

Other abnormal findings seen with the otoscope include:

a hole (perforation) in the eardrum (depending on the cause eardrum perforations can heal remarkably well)

The appearance of the eardrum in acute otitis media is dependent on the time that the infection has been present. Typically, the eardrum becomes red or yellow in appearance and is opaque with indistinct landmarks – it can appear to be bulging towards the viewer. Insufflation may show decreased mobility.

Sometimes in acute otitis media the eardrum will burst, allowing the pressure (and the pain) to reduce. Then one can often see the tear in the drum, as well as the discharge in the outer ear. In the majority of people, such a tear will heal completely.

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